Opportunistic fungal infections, namely involving Candida species,
constitute a hot topic for scientific researchers. The present work aims to
access antifungal potential of plant-derived phenolic extracts against
planktonic cells and biofilms of Candida species. Eucalyptus globulus
Labill. (blue gum), Glycyrrhiza glabra L. (licorice), Juglans regia L.
(walnut) and Salvia officinalis L. (sage) evidenced to be the most effective
Candida growth inhibitors, using disc diffusion assay. Minimal inhibitory
(MIC) and minimal fungicidal (MFC) concentrations, and chemical
composition of extracts by using HPLC-DAD-ESI/MS were also
determined. Blue gum and walnut mainly exerted fungistatic potential,
while sage exerted an interesting anti-Candida potential. However, the
most prominent candidacidal potential was observed to licorice extract,
being achieved the lowest MIC and MFC values. The candidacidal
potential of these phenolic extracts was mainly attributed to their high
abundance in flavonoids, mainly flavones: luteolin (sage) and apigenin
derivatives (licorice), and flavanones: liquiritin derivatives (licorice). In
order to deepen the knowledge on the most effective extract, its ability to
inhibit biofilm formation was evaluated. Overall, a double concentration of
MFC value was necessary to achieve similar results in biofilms. Flow
cytometry assays were also carried out, and the obtained results revealed
that primary lesion of cellular membrane appear to be most relevant
mode of action. Thus, plant derived phenolic compounds evidence a
promising potential to combat Candida species biofilms, both individually
or combined with conventional therapy
